The present invention relates to a control system for the operation of a hydraulic tilt system for a marine outboard engine and more particularly to a control system that allows for the slow trim or fast tilt of the marine drive unit and also senses and prevents the uncontrolled rapid upward movement of the drive unit.
A typical outboard drive unit is attached to the stern of a marine vessel by means of a vertically pivotable support bracket that allows the drive unit to be selectively tilted downwardly into, or upwardly out of, the water. In order to perform satisfactorily, the drive unit should preferably be capable of being locked in its down position so that the drive unit does not swing upwardly due to the thrust of the propeller when the vessel is driven in the reverse direction. The locking system should preferably also prevent the drive unit from being swung upwardly by the resistance of the water when the vessel suddenly decelerates or stops. In order to prevent or at least minimize damage to the drive unit, however, the locking system preferably should automatically release and allow the drive unit to swing upwardly in the event of a collision with a submerged obstacle. The locking system preferably should also be selectively releasable by the operator so that the drive unit may be tilted out of the water for landing or storage. The locking system should also allow for the trimming of the drive unit while underway and for placing the drive unit in a shallow water drive tilt position as well as being adjustable in both forward and reverse modes.
In the past, these functions have been performed by means of complex interconnected mechanical linkages and springs such as shown in U.S. Pat. Nos. 4,064,824; 4,052,952; 3,999,502; 3,983,835; 3,888,203; 3,863,592; 3,839,986; Re.27,932; 3,722,455; 3,434,450; 3,434,448; and 3,285,221. Some of these systems have substituted hydraulic or gas pressurized hydraulic apparatus for such linkages but have been unable to adequately perform the required functions.
Systems such as that shown in U.S. Pat. No. 4,493,659 have been utilized to overcome some of the shortcomings present in earlier systems but systems such as these do not provide all of the functions desired.